The biotech community has been trying to improve on the original Green Fluorescent Protein (GFP) for nearly 20 years, but there appears to be no better innovator when it comes to protein engineering than nature herself. Will a newly discovered fluorescent protein replace GFP? Find out...

Since James Remington’s group first published the crystal structure of the
original Aequora victoria GFP in 1996, researchers have engineered
more than 250 variants of the protein. Early modifications significantly
improved fluorescence intensities and biophysical properties, but recently
developed fluorescent proteins appear to have reached an upper limit in
terms of brightness.

Most advances in brightness have come through modification of three key GFP
residues, but Dimitri Deheyn, associate researcher at the Scripps
Institution of Oceanography at University of California, San Diego, needed a
different approach if he planned to burst through the brightness ceiling.

Rather than continuing to mutate those 3 residues, Deheyn and his colleagues
turned to other marine organisms, examining 16 different GFPs naturally
co-expressed in the cephalochordate Amphioxus. “This is a rare opportunity
since most organisms only have one, or maybe a couple of FPs,” he explained.
“We were looking to screen as many invertebrates as possible for [brighter]
FPs, and when we saw one of the Amphioxus GFPs, it was so much brighter.”

They next compared the photonic, biophysical, and structural properties of a
very bright (bfloGFPa1) and very dim (bfloGFPc1) Amphioxus GFP to Aequora eGFP.
While they found that the bfloGFPs share similar architectures, excitation
spectra, and emission spectra with eGFP, some critical structural
differences in the molecular environment around 3 residues of the bfloGFPa1
chromophore made it 3.5× brighter than eGFP and almost 1000× brighter than
bfloGFPc1.

Rather than adopting bfloGFPa1 for biological experiments, Deheyn expects that
the research community will engineer similar changes to the Aequora GFP
chromophore, since it is so well established. In fact, he has already had
several requests for details of the Aequora GFP substitutions.
According to Deheyn, brighter GFPs should be available very soon as long as
there are no unforeseen problems, such as solubility, that arise when
incorporating the changes.